Label-free quantitative proteomics reveals aberrant expression levels of LRG, C9, FN, A1AT and AGP1 in the plasma of patients with colorectal cancer.

BACKGROUND: Colorectal cancer (CRC) is one of the major causes of cancer-related death worldwide. Although commercial biomarkers of CRC are currently available, they are still lacking in terms of sensitivity and specificity; thus, searching for reliable blood-based biomarkers are important for the primary screening of CRC. METHODS: Plasma samples of patients with non-metastatic (NM) and metastatic (M) CRC and healthy controls were fractionated using MARS-14 immunoaffinity chromatography. The flow-through and elute fractions representing low- and high-abundant proteins, respectively, were analyzed by label-free quantitative proteomics mass spectrometry. The functional analysis of the proteins with greater than 1.5-fold differential expression level between the CRC and the healthy control groups were analyzed for their biological processes and molecular functions. In addition, the levels of plasma proteins showing large alterations in CRC patients were confirmed by immunoblotting using two independent cohorts. Moreover, receiver operating characteristic (ROC) curve analysis was performed for individual and combinations of biomarker candidates so as to evaluate the diagnostic performance of biomarker candidates. RESULTS: From 163 refined identifications, five proteins were up-regulated and two proteins were down-regulated in NM-CRC while eight proteins were up-regulated and three proteins were down-regulated in M-CRC, respectively. Altered plasma proteins in NM-CRC were mainly involved in complement activation, while those in M-CRC were clustered in acute-phase response, complement activation, and inflammatory response. Results from the study- and validation-cohorts indicate that the levels of leucine-rich alpha-2-glycoprotein-1(LRG), complement component C9 (C9), alpha-1-acid glycoprotein 1 (AGP1), and alpha-1-antitrypsin (A1AT) were statistically increased, while fibronectin (FN) level was statistically decreased in CRC patients compared to healthy controls, with most alterations found in a metastatic stage-dependent manner. ROC analysis revealed that FN exhibited the best diagnostic performance to discriminate CRC patients and healthy controls while AGP1 showed the best discrimination between the disease stages in both cohorts. The combined biomarker candidates, FN + A1AT + AGP1, exhibited perfect discriminatory power to discriminate between the CRC population and healthy controls whereas LRG + A1AT + AGP1 was likely to be the best panel to discriminate the metastatic stages in both cohorts. CONCLUSIONS: This study identified and quantified distinct plasma proteome profiles of CRC patients. Selected CRC biomarker candidates including FN, LRG, C9, A1AT, and AGP1 may be further applied for screening larger cohorts including disease groups from other types of cancer or other diseases.

JAK2/STAT3­mediated dose­dependent cytostatic and cytotoxic effects of sesquiterpene lactones from Gymnanthemum extensum on A549 human lung carcinoma cells.

Due to drug resistance and disease recurrence, lung cancer remains one of the primary cancer­related causes of death in both men and women worldwide. In addition, lung cancer is clinically silent and thus most patients are at an advanced stage at the time of diagnosis. The limited efficiency of current conventional chemotherapies necessitates the search for novel effective anticancer agents. The present study demonstrated the anti­proliferative effect and apoptosis­inducing activity of three sesquiterpene lactones isolated from Gymnanthemum extensum, vernodalin (VDa), vernolepin (VLe) and vernolide (VLi), on A549 human lung cancer cells. Treatment with sub­cytotoxic doses (cell viability remaining >75%) of VDa, VLe and VLi, arrested progression of the A549 cell cycle at the G0/G1 phase, while cytotoxic doses of the three compounds induced G2/M phase arrest and apoptosis. Mechanistic studies revealed that VDa, VLe and VLi may exert their anti­tumor activity through the JAK2/STAT3 pathway. Molecular docking analysis confirmed that VDa, VLe and VLi formed hydrogen bonds with the FERM domain of JAK2 protein. Overall, the present study highlighted the potential therapeutic value of VDa, VLe and VLi to be further developed as anticancer agents for the treatment of lung cancer.

Global Analysis of Protein Expression in A549 Cells After Prolonged Nicotine Exposure by Using Label-free Quantification.

BACKGROUND/AIM: Lung cancer is the leading cause of cancer death worldwide. Cigarette smoke is the most important risk factor for cancer development. Growing evidence indicates that prolonged nicotine exposure is a potential factor associated with tumorigenesis. Here, the effect of prolonged nicotine exposure on A549 cells was investigated, using label-free quantitative proteomics. MATERIALS AND METHODS: Selection of an invasive subpopulation from the A549 cell line was performed to reveal the differential expression of proteins in relation to prolonged nicotine exposure, using Boyden chamber assays in combination with a proteomics approach. RESULTS: One hundred proteins from the NicoA549-L5 subline showed significant change in expression compared to those from the A549-L5 subline and their A549 parental cell line. Heat shock protein, protein disulfide isomerase A3, profilin-1 and legumain were expressed at higher levels in A549 cells after prolonged nicotine exposure. CONCLUSION: These aberrant proteins might serve as novel cancer biomarkers for cigarette smokers.

Aberrant RL2 O-GlcNAc antibody reactivity against serum-IgA1 of patients with colorectal cancer.

O-GlcNAcylation, a single attachment of N-acetylglucosamine (GlcNAc) on serine and threonine residues, plays important roles in normal and pathobiological states of many diseases. Aberrant expression of O-GlcNAc modification was found in many types of cancer including colorectal cancer (CRC). This modification mainly occurs in nuclear-cytoplasmic proteins; however, it can exist in some extracellular and secretory proteins. In this study, we investigated whether O-GlcNAc-modified proteins are present in serum of patients with CRC. Serum glycoproteins of CRC patients and healthy controls were enriched by wheat germ agglutinin, a glycan binding protein specifically binds to terminal GlcNAc and sialic acid. Two-dimensional gel electrophoresis, RL2 O-GlcNAc immunoblotting, affinity purification, and mass spectrometry were performed. The results showed that RL2 O-GlcNAc antibody predominantly reacted against serum immunoglobulin A1 (IgA1). The levels of RL2-reacted IgA were significantly increased while total IgA were not different in patients with CRC compared to those of healthy controls. Analyses by ion trap mass spectrometry using collision-induced dissociation and electron-transfer dissociation modes revealed one O-linked N-acetylhexosamine modification site at Ser268 located in the heavy constant region of IgA1; unfortunately, it cannot be discriminated whether it was N-acetylglucosamine or N-acetylgalactosamine because of their identical molecular mass. Although failed to demonstrate unequivocally it was O-GlcNAc, these data indicated that serum-IgA had an aberrantly increased reactivity against RL2 O-GlcNAc antibody in CRC patients. This specific glycosylated form of serum-IgA1 will expand the spectrum of aberrant glycosylation which provides valuable information to cancer glycobiology.

Glycoproteomic Analysis Reveals Aberrant Expression of Complement C9 and Fibronectin in the Plasma of Patients with Colorectal Cancer.

Colorectal cancer (CRC) is a major cause of cancer mortality. Currently used CRC biomarkers provide insufficient sensitivity and specificity; therefore, novel biomarkers are needed to improve the CRC detection. Label-free quantitative proteomics were used to identify and compare glycoproteins, enriched by wheat germ agglutinin, from plasma of CRC patients and age-matched healthy controls. Among 189 identified glycoproteins, the levels of 7 and 15 glycoproteins were significantly altered in the non-metastatic and metastatic CRC groups, respectively. Protein-protein interaction analysis revealed that they were predominantly involved in immune responses, complement pathways, wound healing and coagulation. Of these, the levels of complement C9 (C9) was increased and fibronectin (FN1) was decreased in both CRC states in comparison to those of the healthy controls. Moreover, their levels detected by immunoblotting were validated in another independent cohort and the results were consistent with in the study cohort. Combination of CEA, a commercial CRC biomarker, with C9 and FN1 showed better diagnostic performance. Interestingly, predominant glycoforms associated with acetylneuraminic acid were obviously detected in alpha-2 macroglobulin, haptoglobin, alpha-1-acid glycoprotein 1, and complement C4-A of CRC patient groups. This glycoproteomic approach provides invaluable information of plasma proteome profiles of CRC patients and identification of CRC biomarker candidates.

Urinary biomarkers for the diagnosis of cervical cancer by quantitative label-free mass spectrometry analysis.

Due to the invasive procedure associated with Pap smears for diagnosing cervical cancer and the conservative culture of developing countries, identifying less invasive biomarkers is of great interest. Quantitative label-free mass spectrometry was performed to identify potential biomarkers in the urine samples of patients with cervical cancer. This technique was used to study the differential expression of urinary proteomes between normal individuals and cancer patients. The alterations in the levels of urinary proteomes in normal and cancer patients were analyzed by Progenesis label-free software and the results revealed that 60 proteins were upregulated while 73 proteins were downregulated in patients with cervical cancer. This method could enrich high molecular weight proteins from 100 kDa. The protein-protein interactions were obtained by Search Tool for the Retrieval of Interacting Genes/Proteins analysis and predicted the biological pathways involving various functions including cell-cell adhesion, blood coagulation, metabolic processes, stress response and the regulation of morphogenesis. Two notable upregulated urinary proteins were leucine-rich α-2-glycoprotein (LRG1) and isoform-1 of multimerin-1 (MMRN1), while the 3 notable downregulated proteins were S100 calcium-binding protein A8 (S100A8), serpin B3 (SERPINB3) and cluster of differentiation-44 antigen (CD44). The validation of these 5 proteins was performed by western blot analysis and the biomarker sensitivity of these proteins was analyzed individually and in combination with receiver operator characteristic curve (ROC) analysis. Quantitative mass spectrometry analysis may allow for the identification of urinary proteins of high molecular weight. The proteins MMRN1 and LRG1 were presented, for the first time, to be highly expressed urinary proteins in cervical cancer. ROC analysis revealed that LRG1 and SERPINB3 could be individually used, and these 5 proteins could also be combined, to detect the occurrence of cervical cancer.

Phosphoproteome Profiling of Isogenic Cancer Cell-Derived Exosome Reveals HSP90 as a Potential Marker for Human Cholangiocarcinoma.

The northeastern region of Thailand is well known to have a high incidence and mortality of cholangiocarcinoma (CCA). Protein phosphorylation status has been reported to reflect a key determinant of cellular physiology, but identification of phosphoproteins can be a problem due to the presence of phosphatase. Exosomes are stable toward circulating proteases and other enzymes in human blood and can be recognized before the onset of cancer progression. Here an in vitro metastatic model of isogenic CCA cells is used to provide insight into the phosphorylation levels of exosomal proteins derived from highly invasive cells. Gel-based and gel-free proteomics approaches are used to reveal the proteins differentially phosphorylated in relation to tumor cell phenotypes. Forty-three phosphoproteins are identified with a significant change in phosphorylation level. Phos-tag western blotting and immunohistochemistry staining are then employed to validate the candidate phosphoproteins. Heat shock protein 90 is successfully confirmed as being differentially phosphorylated in relation to tumor malignancy. Importantly, the aberrant phosphorylation of exosomal proteins might serve as a promising tool for the development of a biomarker for metastatic CCA.

Secretomic profiling of cells from hollow fiber bioreactor reveals PSMA3 as a potential cholangiocarcinoma biomarker.

Cholangiocarcinoma (CCA), derived from the bile duct, occurs with a relatively high incidence in Northeast Thailand. Early diagnosis is still hampered by the lack of sufficient biomarkers. In recent years, biomarker discovery using secretomes has provided interesting results, including our studies on CCA secretomes, especially with three-dimensional cell cultures. Thus, cells cultured using the hollow fiber bioreactor (HFB) with 20 kDa molecular weight cut-off (MWCO) yielded higher quality and quantity of secretomes than those from conditioned media of the monolayer culture (MNC) system. In this study, we employed the HFB culture system with 5 kDa MWCO and compared conditioned media from the HFB and MNC systems using two-dimensional gel electrophoresis, followed by identifying proteins of interest by liquid chromatography and mass spectrometry (LC/MS/MS). Two out of 4 spots of NGAL or lipocalin-2 were found to show highest increase in expression of 19.93-fold and 18.79-fold in HFB compared to MNC. Interestingly, all 14 proteasome subunits including proteasome subunit α type-1 to type-7 and ß type-1 to type-7 showed 2.92-fold to 12.13-fold increased expression in HFB. The protein-protein interactions of upregulated proteins were predicted, and one of the main interaction clusters involved 20S proteasome subunits. Proteasome activity in the HFB conditioned media was also found to be higher than that in MNC conditioned media. Three types of proteasome subunit were also validated by immunoblotting and showed higher expression in the HFB system compared to MNC system. Proteasome subunit α type-3 (PSMA3) showed the highest level in plasma of cholangiocarcinoma patients compared to normal and hepatocellular carcinoma patients by immunodetection, and is of interest as a potential biomarker for cholangiocarcinoma.